1. Field of the Invention
The present invention relates to an arrangement for the guidance or conductance of a beam during the treatment of a workpiece with a laser, especially during a surface treatment by the laser beam, through the intermediary of mirrors which are interposed in the path of the beam intermediate a laser source and the workpiece.
2. Discussion of the Prior Art
An arrangement of that type is known, in the constructional configuration of a so-called manipulable focusing optic, from the disclosure of U.S. Pat. No. 3,986,767. In particular, the present invention relates to an arrangement for surface treatments through the utilization of lasers; for example, such as have already become known from the disclosures of German Patent 35 09 582 or U.S. Pat. No. 4,451,299. With respect to the surface treatment of a workpiece, in which the treatment is based on a localized heating, there are encountered technological problems which are in general similar to those encountered during the autogenous welding to the extent that, in the direction of forward displacement along the treatment front, due to the heat conductivity of the material there is desired the presence of an excessive supplying of heat for effectuating the rapid heating up to the metallurgically required temperature, while in order to avoid any undesired reactions during the cooling down of the material (along the rear side with respect to the advancing movement during treatment), it is intended to obtain a delayed and within certain bounds controlled temperature dropoff, such as would be controllable through localized reduction in the supply of energy. In connection with the foregoing, reference is made to the laser power distribution and period of effectiveness which is sought after with respect to the specified process, as treated in the article "Laseranwendungen in der Fertigungstechnik", by C. Schmitz-Justen et al., in the publication "Lasertechnologie", page 25; and also referring to the middle of page 482 in OPTOELEKTRONIK MAGAZIN, Vol. 4, No. 5, 1988. In essence, it would not be ideal to allow the beam cross-section which is delivered from the laser source to directly act on the surface of the workpiece, inasmuch as within the present context, this would not occasion the formation of a desirable temperature profile in dependence upon the conditions of advancing movement along the treatment zone. In addition thereto, high-energy laser sources, such as are employed for a highly effective workpiece treatment, operate with astable resonators; in effect, which couple out or neutralize a ring-shaped beam cross-section. However, the movement of a ring-shaped beam image across the surface of the workpiece would lead to the situation that along the side edges of the path of treatment, because of the tangential overlapping, there would be encountered excessively high temperatures whereas inbetween thereof, due to the distance between the front-sided and rear-sides arcuate portion of the ring, there would then reign a lower temperature. This would be considerably remote from the intended temperature distributions, as has been qualitatively discussed hereinabove. In effect, for the high-energy laser technology there is known the applications of faceted mirrors for exerting an influence over individual beam cross-sections in relationship with adjacent beam portions (for example, offered for sale as VA-Mo-segmented mirror by the NIPPON Mining Co., Ltd.); however, the intended random correlatability of the energy focus or focal point to the actual reaction of the workpiece surface cannot be achieved through such fixed geometric beam tasks.